Chromosomal and in vitro culture studies in a case of primary plasma cell leukemia

We present a cytogenetic study of a case of primary plasma cell leukemia (PCL) whose plasma cells were cultured in vitro with different mitogens. Cytogenetic studies demonstrated a reduction of the genome, monosomy of chromosomes 8, 13, and 22 being the most frequent. Neither structural changes nor marker chromosomes were observed. The hypodiploid karyotype was confirmed and confined to the neoplastic clone (lambda positive cells) by the MAC (Morphology, Antibody, Chromosome) method, which allows a simultaneous study of chromosomes, cell morphology, and immunologic phenotype. Stimulating the culture of plasmocytes in vitro with IL-6 + PHA, only normal metaphases could be obtained; on the other hand, a large number of abnormal metaphases were observed with the use of LPS as a mitogen. A surprisingly high yield of metaphases was obtained in this case, contrary to the rule in the in vitro growth of plasmocytic proliferations. Possible explanations of this fact are considered.